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  • 1.
    Angerbjörn, Anders
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Pehrson, A.
    Factors Influencing Winter Food Choice by Mountain Hares (Lepus-Timidus L) on Swedish Coastal Islands1987In: Canadian Journal of Zoology, ISSN 0008-4301, E-ISSN 1480-3283, Vol. 65, no 9, p. 2163-2167Article in journal (Refereed)
    Abstract [en]

    In mainland areas, mountain hares seem unable to survive on a single browse species. However, mountain hares on islands off the west coast of Sweden rely almost entirely on a plain heather diet during winter. Herein, we give as a possible explanation for this phenomenon that the high concentration of sodium in the heather in the coastal areas can buffer the high sodium excretion otherwise observed in hares feeding on heather under experimental conditions. Furthermore, hares selected heather with the highest nitrogen and phosphorus contents. We argue that the pattern of food choice exhibited by the hares in the coastal area is to be expected in homogenous habitats where hares rely on one dominant food species. In heterogenous habitats, the possibility of food selection on a nutritional level is to a considerable extent overridden by effects of digestibility and concentration of secondary compounds in the different food plants available.

  • 2.
    Dalerum, Fredrik
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. University of Oviedo, Spain; University of Pretoria, South Africa.
    Freire, S.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Lecomte, N.
    Lindgren, A.
    Meijer, Tomas
    Stockholm University, Faculty of Science, Department of Zoology.
    Pečnerová, Patricia
    Stockholm University, Faculty of Science, Department of Zoology. Swedish Museum of Natural History, Sweden.
    Dalén, Love
    Stockholm University, Faculty of Science, Department of Zoology. Swedish Museum of Natural History, Sweden.
    Exploring the diet of arctic wolves (Canis lupus arctos) at their northern range limit2018In: Canadian Journal of Zoology, ISSN 0008-4301, E-ISSN 1480-3283, Vol. 96, no 3, p. 277-281Article in journal (Refereed)
    Abstract [en]

    The grey wolf (Canis lupus Linnaeus, 1758) is one of the most widespread large carnivores on Earth, and occurs throughout the Arctic. Although wolf diet is well studied, we have scant information from high Arctic areas. Global warming is expected to increase the importance of predation for ecosystem regulation in Arctic environments. To improve our ability to manage Arctic ecosystems under environmental change, we therefore need knowledge about Arctic predator diets. Prey remains in 54 wolf scats collected at three sites in the high Arctic region surrounding the Hall Basin (Judge Daly Promontory, Ellesmere Island, Canada, and Washington Land and Hall Land, both in northwestern Greenland) pointed to a dietary importance of arctic hare (Lepus arcticus Ross, 1819; 55% frequency of occurrence) and muskoxen (Ovibos moschatus (Zimmermann, 1780); 39% frequency of occurrence), although we observed diet variation among the sites. A literature compilation suggested that arctic wolves (Canis lupus arctos Pocock, 1935) preferentially feed on caribou (Rangifer tarandus (Linnaeus, 1758)) and muskoxen, but can sustain themselves on arctic hares and Greenland collared lemmings (Dicrostonyx groenlandicus (Traill, 1823)) in areas with limited or no ungulate populations. We suggest that climate change may alter the dynamics among wolves, arctic hare, muskoxen, and caribou, and we encourage further studies evaluating how climate change influences predator-prey interactions in high Arctic environments.

  • 3.
    Elmhagen, Bodil
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Tannerfeldt, M.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Food-niche overlap between arctic and red foxes2002In: Canadian Journal of Zoology, ISSN 0008-4301, E-ISSN 1480-3283, Vol. 80, no 7, p. 1274-1285Article in journal (Refereed)
    Abstract [en]

    Arctic foxes (Alopex lagopus) in Fennoscandia have retreated to higher altitudes on the mountain tundra, possibly because of increased competition with red foxes (Vulpes vulpes) at lower altitudes. In this study we compare summer food niches of the two species in mountain tundra habitat. Arctic foxes consumed lemmings more often than red foxes did, while red foxes consumed field voles and birds more often. Yet despite substantial variation in the diet of each species among summers, food-niche overlaps between the species were consistently high in most summers, as arctic and red foxes responded similarly to temporal changes in prey availability. Occurrences of field voles and birds in fox scats were negatively Correlated with altitude, while the occurrences of lemmings tended to increase with altitude. Since arctic foxes bred at higher altitudes than red foxes, the differences between arctic and red fox diets were better explained by altitudinal segregation than by differences between their fundamental food niches. Arctic foxes should therefore endeavour to use the more productive hunting grounds at the lower altitudes of their former range, but interference competition with red foxes might decrease their access to these areas, and consequently cause a decrease in the size of in their realised niche.

  • 4.
    Erlandsson, Rasmus
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Meijer, Tomas
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Wagenius, Sofie
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Indirect effects of prey fluctuation on survival of juvenile arctic fox (Vulpes lagopus): a matter of maternal experience and litter attendance2017In: Canadian Journal of Zoology, ISSN 0008-4301, E-ISSN 1480-3283, Vol. 95, p. 239-246Article in journal (Refereed)
    Abstract [en]

    Reproductive experience affects juvenile survival in a wide range of species with possible links to differences in foraging capacity and predation. Using supplementary feeding, we aimed to limit direct effect of prey abundance to investigate indirect effects of small-rodent availability and maternal experience on juvenile summer survival rates in an endangered population of arctic fox (Vulpes lagopus (L., 1758)). We used data spanning 7 years, included a complete small-rodent cycle, comprising 49 litters and 394 cubs. The effect of small-rodent abundance on juvenile survival depended on maternal breeding experience. Cubs born by first-time-breeding females had lower survival rate when small-rodent abundance was low compared with juveniles born to experienced mothers who remained unaffected. It was unlikely due to starvation, as physical condition was unrelated to survival. Instead, we favour the explanation that intraguild predation was an important cause of mortality. There was a negative relationship between survival and amount of time cubs were left unattended, suggesting that parental behaviour affected predation. We propose that a prey switch related to small-rodent abundance caused fluctuations in intraguild predation pressure and that inexperienced females were less able to cope with predation when small rodents were scarce.

  • 5.
    Mellbrand, Kajsa
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Hambäck, Peter
    Stockholm University, Faculty of Science, Department of Botany.
    Coastal niches for terrestrial predators: a stable isotope study.2010In: Canadian Journal of Zoology, ISSN 0008-4301, E-ISSN 1480-3283, Vol. 88, p. 1077-1085Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was to identify the use of marine versus terrestrial food items by terrestrial arthropod predators on Baltic Sea shores. The inflow of marine nutrients in the area consists mainly of marine algal detritus and emerging aquatic insects (e.g., chironomids). Diets of coastal arthropods were examined using carbon and nitrogen stable isotope analysis in a two source mixing model. The results suggest that spiders are the terrestrial predators mainly utilizing nutrients and energy of marine origin on Baltic Sea shores, whereas insect predators such as beetles and heteropterans mainly utilize nutrients and energy derived from terrestrial sources, possibly owing to differences in hunting behaviour. That spiders are the predators which benefit the most from the marine inflow suggest that eventual effects of marine subsidies for the coastal ecosystem as a whole are likely mediated by spiders.

  • 6.
    Norén, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Hersteinsson, Pall
    Samelius, Gustaf
    Eide, Nina E.
    Fuglei, Eva
    Elmhagen, Bodil
    Stockholm University, Faculty of Science, Department of Zoology.
    Dalén, Love
    Stockholm University, Faculty of Science, Department of Zoology.
    Meijer, Tomas
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    From monogamy to complexity: social organization of arctic foxes (Vulpes lagopus) in contrasting ecosystems2012In: Canadian Journal of Zoology, ISSN 0008-4301, E-ISSN 1480-3283, Vol. 90, no 9, p. 1102-1116Article in journal (Refereed)
    Abstract [en]

    Canids display pronounced intraspecific variation in social organization, ranging from single breeding females to large and complex groups. Despite several hypotheses in this matter, little is understood about the ecological factors underlying this flexibility. We have used the arctic fox (Vulpes lagopus (L., 1758)) to investigate how contrasting ecosystem conditions concerning resources and predation influence group formation. We predicted that complex groups are more common in resource-rich ecosystems with predators, whereas simple groups occur in more marginal ecosystems without predators. Samples from 54 groups were collected from four populations of arctic foxes with contrasting prey resources and predation and these samples were genotyped in 10 microsatellite loci. We found considerable variation between ecosystems and a significant relationship between resources and formation of complex groups. We conclude that sufficient amounts of food is a prerequisite for forming complex groups, but that defense against predation further increases the benefits of living in larger groups. We present a conceptual model suggesting that a trade-off between the cost of resource depletion and the benefits obtained for guarding against predators explain the differences in social organization. The variable ecology of  the arctic foxes makes it is a plausible model species for understanding the connection between ecology and social organization also in other species.

  • 7.
    Nässel, Dick R.
    Stockholm University, Faculty of Science, Department of Zoology.
    Insulin producing cells and their regulation in physiology and behavior of Drosophila2012In: Canadian Journal of Zoology, ISSN 0008-4301, E-ISSN 1480-3283, Vol. 90, no 4, p. 476-488Article, review/survey (Refereed)
    Abstract [en]

    Insulin-like peptide signaling regulates development, growth, reproduction, metabolism, stress resistance, and life span in a wide spectrum of animals. Not only the peptides, but also their tyrosine kinase receptors and the downstream signaling pathways are conserved over evolution. This review summarizes roles of insulin-like peptides (DILPs) in physiology and behavior of Drosophila melanogaster Meigen, 1830. Seven DILPs (DILP1-7) and one receptor (dInR) have been identified in Drosophila. These DILPs display cell and stage specific expression patterns. In the adult, DILP2, 3, and 5 are expressed in insulin-producing cells (IPCs) among the median neurosecretory cells of the brain, DILP7 in 20 neurons of the abdominal ganglion, and DILP6 in the fat body. The DILPs of the IPCs regulate starvation resistance, responses to oxidative and temperature stress, and carbohydrate and lipid metabolism. Furthermore, the IPCs seem to regulate feeding, locomotor activity, sleep and ethanol sensitivity, but the mechanisms are not elucidated. Insulin also alters the sensitivity in the olfactory system that affects food search behavior, and regulates peptidergic neurons that control aspects of feeding behavior. Finally, the control of insulin production and release by humoral and neuronal factors is discussed. This includes a fat body derived factor and the neurotransmitters GABA, serotonin, octopamine, and two neuropeptides.

  • 8.
    Shirley, Mark
    et al.
    Newcastle University.
    Elmhagen, Bodil
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Lurz, Peter
    Newcastle University.
    Rushton, Steve
    Newcastle University.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Modelling the spatial population dynamics of arctic foxes: the effects of red foxes and microtine cycles2009In: Canadian Journal of Zoology, ISSN 0008-4301, E-ISSN 1480-3283, Vol. 87, p. 1170-1183Article in journal (Refereed)
    Abstract [en]

    The Fennoscandian arctic fox Vulpes lagopus (L., 1758) population is critically endangered, possibly because of increased interference competition from red foxes Vulpes vulpes (L., 1758) and fading cycles in microtine rodents, which cause food shortage. It is not known how these factors drive arctic fox population trends. To test their role in arctic fox decline, we developed a spatially-explicit and individual-based model that allowed us to simulate fox interactions and food availability in a real landscape. A sensitivity analysis revealed that simulated arctic fox population size and den occupancy were strongly correlated with fecundity and mortality during the microtine crash phase, but also with red fox status. Model simulations suggested that arctic fox population trends depended on microtine cycles and that arctic fox distributions were restricted by red fox presence. We compared the model predictions with field data collected at Vindelfjällen, Sweden. The model recreated the observed arctic fox trend only with the inclusion of arctic fox avoidance of red fox home ranges. The results indicate that avoidance behaviours can affect population trends and hence, that relatively small numbers of red foxes can have a strong negative impact on arctic fox population size and distribution.

1 - 8 of 8
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